To assess the potential toxicity of mistletoe ingestion, data were collected on 14 cases of ingestion of one to three berries or one or two leaves of American mistletoe (Phoradendron sp) from 1982 to 1985. Eleven patients ingested berries and three ingested leaves; none became symptomatic. Nine patients were observed at home without intervention except poison center telephone follow-up. Five had induced emesis, including two who were referred to emergency departments for evaluation, where no findings other than ipecac-induced vomiting were noted. Also reviewed were data on a total of 318 cases of mistletoe ingestion reported to the Food and Drug Administration Poison Control case reporting system between 1978 and 1983 (n = 177) and the American Association of Poison Control Centers national data collection system (n = 141) in 1984. The majority remained asymptomatic and no deaths were recorded. These data allow the conclusion that ingestion of one to three mistletoe berries or one or two leaves is unlikely to produce serious toxicity.